As a digital camera has become small, compact, and inexpensive, consequently, the digital camera could be embedded in handheld electronic devices such as cellular phones, smart phones, tablet computers, personal digital assistants and so forth. The diminutive nature of such camera allows the camera to become a convenient and popular additional feature of portable consumer electronic devices. However, the portability of such electronic devices may have prevented many more sophisticated uses or structures to be included for such cameras. For example, fixed focal length lenses and small sensors would typically be used for such cameras since an optical zoom lens may be too heavy and require more physical depths than the body of the handheld electronic device would permit, and yet the speed of an auto-focus procedure is highly dependent on the maximum aperture offered by the lens. Therefore, there is a need for an effective auto-focus method for such handheld electronic device.